Remove legacy crates

[PhilippGackstatter]

Description of change

Added

• Add IotaDID::is_placeholder which was required for the updated identity_agent tests and seemed generally useful to have.

Changed

• Remove identity_account.
• Remove examples_legacy.
• Remove most of identity_account_storage except
  • src/stronghold/* (Stronghold wrapper types)
  • src/types/encryption/* (encryption types)
  • src/utils/crypto.rs (PBKDF2 key derivation)
• Remove dependency of identity_agent on identity_account and re-add it to the root Cargo.toml.
• Remove most of bindings/wasm/src/account/.
• Comment out CI checks for stronghold-nodejs bindings because it depended on identity_account_storage.

Links to any relevant issues

n/a

Type of change

Add an x to the boxes that are relevant to your changes.

• Bug fix (a non-breaking change which fixes an issue)
• Enhancement (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Fix

How the change has been tested

CI runs.

Change checklist

Add an x to the boxes that are relevant to your changes.

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[olivereanderson]

LGMT.

Thanks for taking the time to adapt identity-agent.

Could you please test building the wiki on this branch before merging?